Safety mechanism for machine tools

ABSTRACT

A safety mechanism for indexing machines, e.g., rotary dial type or, transfer machines, of the type having a multihead tool carrier, bushing plate, and fixture, includes a normally closed switching unit in electrical series with the transferring or indexing circuit and is mounted on the multihead. The mechanism further includes a flex cable mounted on the bushing plate, having means associated therewith for closing the switching unit; the flex cable being of a preselected length such that an open circuit is provided unless the bushing plate is in its normal position on the multihead.

United States Patent 1191 Biafore 1 SAFETY MECHANISM FOR MACHINE TOOLS [76] Inventor: John .1. Biafore, 38653 Foxcroft,

Harrison, Mich. 48043 [22] Filed: Oct. 16, 1972 [21] Appl. No: 298,015

[52] US. Cl ZOO/61.58 R, 408/710, 200/161 [51] Int. Cl. H0111 3/16 [58] Field of Search...-.....' 200/51 R, 51.09, 51.1,

153 T; 192/129 R, 129 A,l3l, 142; 408/710; 339/40 [56] References Cited UNITED STATES PATENTS 2.722.575 11/1955 Dobkin ZOO/61.58 R X 2,768,234 10/1956 Popp ZOO/51.1 X 2.818.480 12/1957 Barker 200/153 T 3.127.597 3/1964 Lewin et a1. ZOO/51.09 X 3,196,293 v Howard 200/61.67 X

[ June 4, 1974 3,204,053 8/1965 Bilek ZOO/51.09 3,381,550 5/1968 Smith 408/710 X 3,536,876 10/1970 Lastinger et a1. 200/161 Primary Examiner-James R. Scott Attorney, Agent, 0rF1'rm-Weiner, Basile and Weintraub 57 ABSTRACT A safety mechanism for indexing machines, e.g., rotary dial type or, transfer machines, of the type having a multihead tool carrier, bushing plate, and fixture, in-

. cludes a normally closed switching unit in electrical series with the transferring or indexingcircuit and is mounted on the multihead. The mechanism further includes a flex cable mounted on the bushing plate, having means associated therewith for closing the switching unit; the flex cable being of a preselected length such that an open circuit is provided unless the bushing plate is in its normal position on the multihead. 1

7 Claims, 4 Drawing Figures 1 I SAFETY MECHANISM FOR MACHINE TOOLS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to safety mechanisms for indexing-type multihead machine tools and, in particular, the present. invention pertains to safety mechanisms for rotary dial type or transfer machines. More particularly the present invention concerns a safety mechanism particularly adapted for use with the considered machine tools whereby transferring or indexing of the machine is prevented unless the bushing plate is engaged with the multihead.

, the like for transferring or otherwise indexing the workpiece to another machine, station, or the like, all of this background being well known to the skilled artisan.

Because of the nature of the work functions performed by the tools, it is incumbent that the tools disposed on a multihead be changed over varying time intervals. During a tool change operation the bushing plate is unlocked and disengaged from the multihead and registered on the fixture to afford easy access to the replacement sought tool. Once the tool change is effected, the bushing plate is to be returned to its normal position, i.e., locked onto the multihead. T often, however, after the tool change has occurred,'the bushing plate is not returned to its normal position by the operator. Thisresults in the machine indexing or transferring with the bushing plate still. engaged with the fixture. When this occurs the tools'are damaged, as is the workpiece, with the concomittant down time, repair costs and the like.

Heretofore known devices adapted to alleviate this situation are deficient in many areas, such as cost, complexity, malfunction and the like. See, inter alia, US. Pat. Nos. 3,208,127; 2,800,543; 3,315,051; and 2,706,544. The present invention, on the other hand, provides a non-complex, easily installed device to alleviate these problems.

SUMMARY OF THE INVENTION 'the bushin plate. and

c. means for opening the normally closed switching unit, the means being carried on one end of the flex cable.

The flex cable is of a preselected length such that only when the bushing plate is engaged with the multihead can the means for closing the switching unit be utilized to achieve closure.

For a more complete understanding of the present invention, reference is made to the following detailed description and accompanying drawing. In the drawing like reference characters refer to like parts throughout the several views in which:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial side elevational view of a multihead tool machine wherein the bushing plate is engaged therewith and the switching mechanism is in a closed circuit;

FIG. 2 is a cross-sectional view of a switching unit in accordance with the present invention with the means for opening the circuit being in electrical connection therewith;

FIG. 3is a perspective view of an alternate embodi ment of the present invention; and

FIG. 4 is a partial circuit diagram for the embodiment of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is depicted therein a tool machine generally indicated at 10. The machine includes a multihead tool carrier 12, a fixture l4 and a bushing plate 16. The bushing plate 16 is journalled on the multihead and is axially displaced therefrom through a spring and guide rod assembly 18, in a man- .ner well-known to the skilled artisan.

and bushing plate disposed therebetween. Also, by the term indexing" is meant either the transferring of a workpiece from station-to-station on the machine or to another machine.

Still referring to FIG. 1, there is shown therein the safety mechanism of the present invention, generally, denoted as 22. The mechanism 22 includes a flex cable 24 and a microswitch assembly 26. More particularly, a mounting bracket 28 is disposed on the bushing plate 16. The bracket 28 is detachably secured to the bushing'plate 16 through threaded connectors or the like, such as, threaded screws or the like.

' The bracket 28 has a retainer means, such as throughbore 30, formed therein. The throughbore, as formed in the bracket, frictionally engages and clamps the cable therein to securedly retain it in position. The.

The socket further, has a medially positioned circumferential groove 42 formed therein which cooperates with a pin detent to retain the pin 40 in the switch assembly 26;

Still referring to FIG. 2, the switch assembly 26 includes a housing 44 in which is disposed a mircoswitch 46. The microswitch is mounted on a seat 48 formed in the interior of the housing. An axial throughbore 50 is provided beneath the seat 48 for receiving and retaining the pin 40. Disposed within the bore 50 is a bushing 52 for inhibiting wear on the throughbore and the pin.

Located proximate the entrance of the throughbore is a pin detent 52 which is mounted in the interior of the housing in an aperture provided therein. A biassing means (n& shown) is located rearwardly of the detent and normally urges it radially inwardly into the interior of the throughbore. Thus, when the pin 40 is inserted into the housing, the detent engages the groove or recess 42 to securely hold the pin position. This obviates the possibility of creating an open circuit due to minor jostling of the multihead or thelike.

The switch-asse bly 26 further includes a vertically disposed plenum 6 which is in communication with the throughbore 50 and into which the pin 40 extends. A biassed switching blade 58, such as a pushbutton blade or the like, is disposed within the plenum and is normally urged downwardly by the biassing means. When the switching blade is urged against the force of the biassing means by contact with the pin, the microswitch is closed. Thus, when the pin engages the switching blade the microswitch is in its normally closed position to provide an operational or closed circuit.

The microswitch 46 can comprise any conventional single pole, single throw switch which has wired thereto, through suitable contacts, a current carrying means, such as cable 60. The cable 60 is connected in series with the main indexing circuit of the machine (not shown). For example, in a transfer machine, the

cable is wired in series with the transfer machine interlock switch. In a rotary or dial machine, the cable is wired in series with the shot bolt switch.

Thus, when the pin 40 is properly positioned there is presented a closed switch which allows the tool machine to function. The pin can only be properly positioned, though, when the bushing plate is in its normal operating position registered on the multihead, due to the length of the flex cable 24. In the event that the bushing plate is not properly positioned, then an open circuit is presented since the length of cable, being so predetermined in length, will prevent the pin from closing the micro switch.

Referring now to FIGS. 2-4, there is shown therein a particularly preferred embodiment of the switch assembly 26. In this embodiment the microswitch 46 comprises a double-pole, single-throw switch. The switching terminals or switches comprise a first normally open switch 116 and a second normally closed switch 118, bothbeing, respectively opened and closed by the movement of the pin 40 in the manner heretofore described.

Extending from the first switch is a pair of lead wires 122, 124 which connects the switch 116 in series to a signalling means 126, such as, an illumination means, siren orthe like which is seated in a mounting 128 formed in the corner 130 for the housing 44, as shown. The signalling means is used to indicate to the operator the (disengagement of the bushing plate from the multi- The normally closed switch 118 is wired in series with the main indexing circuit of the machine through wires 128 and 130, as shown. Thus, when the pin becomes disengaged from the microswitch, the second switch, 118 is opened and contemporaneously the first switch is closed thereby sending current therethrough to the signalling means 126 which is thereupon activated. Thus, when the bushing plate is not in its operating position such occurrance can be instantaneously signalled to the operator.

Return of the bushing plate to its normal position permits re-insertion of the pin, with the contemporaneous closing of the second switch and opening of the first switch.

It is to be further understood in connection with the present invention that all of the connecting wires or lead wires can be color coded to facilitate installation, especially in those preferred instances wherein the safety mechanism is available as a pre-assembled and packaged unit.

Having thus described the invention, what is claimed is:

1. In an indexing machine tool of the type having a fixture, a multihead tool carrier and a bushing plate journalled on the multihead and being axially displaced therefrom, and disengageable therefrom onto the fixture the improvement which comprises:, a safety mechanism therefor, the mechanism comprising in combination:

a. a normally closed switching unit mounted on the multihead, the unit being connected in electrical series with the indexing circuit of the machine tool,

b. a flex cable of predetermined length having one end thereof mounted on the bushing plate,

c. means for opening the switching unit carried on one end of the cable, and wherein d. the bushing plate must be maintained within a predetermined maximum distance from the multihead as determined by the length of the cable to prevent Elie means for opening from being rendered opera- 2. The mechanism of claim 1 which includes visual means for indicating the open condition of the switching unit.

3. The mechanism of claims 2 wherein the switching unit includes a first normally closed switch in electrical series with the indexing circuit and a second normally open switch in electrical communication with the means for indicating, the means for opening being operable to close the second switch, upon the opening of the first switch; the closing of the first switch activating the indicating means, the first switch being electrically in parallel with the second switch.

4. The mechanism of claim 1 wherein the switching unit includes a normally closed microswitch and an actuator, the actuator engaging the means for opening the switching'unit in a normally closed condition.

5. The mechanism of claim 3 wherein the means for opening the switching unit comprises an elongated pin carried on the other end of the flex cable, and which normally engages the switching blade to close the circurt.

6. The mechanism of claim 1 wherein the cable is of a predetermined length such that when the bushing plate is disengaged from the multihead, the means for opening the switching unit is disengaged therefrom, thereby presenting an open circuit.

7. The mechanism of claim 1 which includes audio meansfor indicating the open condition of the switchmg unit. 

1. In an indexing machine tool of the type having a fixture, a multihead tool carrier and a bushing plate journalled on the multihead and being axially displaced therefrom, and disengageable therefrom onto the fixture the improvement which comprises:, a safety mechanism therefor, the mechanism comprising in combination: a. a normally closed switching unit mounted on the multihead, the unit being connected in electrical series with the indexing circuit of the machine tool, b. a flex cable of predetermined length having one end thereof mounted on the bushing plate, c. means for opening the switching unit carried on one end of the cable, and wherein d. the bushing plate must be maintained within a predetermined maximum distance from the multihead as determined by the length of the cable to prevent the means for opening from being rendered operable.
 2. The mechanism of claim 1 which includes visual means for indicating the open condition of the switching unit.
 3. The mechanism of claims 2 wherein the switching unit includes a first normally closed switch in electrical series with the indexing circuit and a second normally open switch in electrical communication with the means for indicating, the means for opening being operable to close the second switch, upon the opening of the first switch; the closing of the first switch activating the indicating means, the first switch being electrically in parallel with the second switch.
 4. The mechanism of claim 1 wherein the switching unit includes a normally closed microswitch and an actuator, the actuator engaging the means for opening the switching unit in a normally closed condition.
 5. The mechanism of claim 3 wherein the means for opening the switching unit comprises an elongated pin carried on the other end of the flex cable, and which normally engages the switching blade to close the circuit.
 6. The mechanism of claim 1 wherein the cable is of a predetermined length such that when the bushing plate is disengaged from the multihead, the means for opening the switching unit is disengaged therefrom, thereby presenting an open circuit.
 7. The mechanism of claim 1 which includes audio means for indicating the open condition of the switching unit. 